The invention relates to a windmill generally of the sail-type, of the same general class as the windmill shown in U.S. Pat. No. 3,995,170.
According to the present invention, it is desired to provide a windmill that provides a high torque without limitations as to size, and which provides maximum efficiency, is easy and inexpensive to construct, and provides "self-reefing", so that it will not be damaged in high winds.
According to the preferred embodiment of the present invention, a windmill is provided that includes a frame having upper and lower frame sections and a plurality of symmetrically disposed mast sections interconnecting the upper and lower frames. While normally the windmill according to the present invention will be a vertical axis windmill, in fact it can have a horizontal axis, or a wide variety of other orientations of its axis of rotation, therefore it is to be understood that the terms "upper" and "lower" as used in the present specification and claims are for reference only, and do not limit the invention to a vertical axis disposition.
The preferred embodiment of the invention further comprises a plurality of substantially quadrate sail members, consisting of three sail members, with the sail members operatively attached to at least one mast section so that they may assume different orientations with respect to each said mast section. The frame is mounted for rotational movement about an axis parallel to the mast sections, the mounting means comprising a central shaft or a stationary circular track with cooperating rollers on the lower frame, and means are provided for transforming rotational movement of the frame into a useful energy form such as electrical energy, mechanical pumping, or the like.
In one embodiment of the invention, the sail members are flexible and are operatively attached to sail masts along one longitudinal edge thereof, and are attached by sheets along the opposite longitudinal edge thereof to sheet masts, each sheet mast being disposed between two sail masts and vice versa. The frame also preferably includes a plurality of spokes, one extending from a central portion of the upper or lower frame section to a mast. Self-reefing is provided for modifying the effective area each sail member presents to the wind in response to wind velocity ("shortening" the sail as wind velocity increases) by means for mounting each of the mast sections for rotation with respect to the upper and lower frame sections about an axis concentric with each mast section, means for mounting each sheet to each sheet mast to take-up and let-out the sheet length in response to rotation of each sheet mast, the means for attaching each sail member to each sail mast providing means for effecting take-up and let-out of the amount of sail in response to rotation of each sail mast, and centrifugal responsive means for effecting coincident rotation of the sail and sheet mast in response to the speed of rotation of the frame. The centrifugal responsive means comprise a weight operatively associated with each lower sheet spoke and a spring for biasing each weight to a predetermined radial position with respect to the lower sheet spoke, a line connected at both ends thereof to the weight and extending around a capstain rigidly attached to the sail mast, a capstain rigidly attached to the sheet mast, and a roller mounted at a radially inward location between the lower sail and sheet spokes. As the velocity of the frame increases, each weight moves radially outward against the bias of the spring to "shorten" the sail associated therewith, and then returns to a more inward radial position under the influence of the spring as the speed of rotation of the frame decreases.
According to another embodiment of the invention, the sails are formed of flexible metal or the like, and each sail is mounted to a sail mast for pivotal movement about the sail mast along the axis of the sail mast by boom means. Speed governing of the windmill is provided by a plurality of hydraulic or pneumatic cylinders, at least one associated with each sail mast and including a pair of stops associated with the boom means for restricting the freedom of movement between about 0.degree. and about 280.degree.. The hydraulic or pneumatic cylinders are controlled by an aerometer which controls a fluid pressure source to effect extension or retraction of the cylinder piston.
It is the primary object of the present invention to provide an efficient, relatively inexpensive, windmill that provides high torque without limitations on size, This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.